Jan 16, Three Master's Thesis Seminars in Computer Science

Kl 13.15: Performance Evaluation of ISO C restrict on the Power Architecture

Författare/Authors: Anton Botvalde, Andreas Larsson

Handledare/Supervisor: Jonas Skeppstedt (LTH)

Examinator/Examiner: Per Andersson (LTH)

Lokal/Room: E:2405

Abstract:

The C99 standard for the C programming language introduced the new type qualifier restrict which acts as a hint for the compiler and the programmer that the specified pointer is not aliased by any other pointer if the pointed to object can be modified. By using restrict on pointers the compiler may, if implemented and allowed, optimize code even further. This thesis investigates how well the C compilers GCC, Clang and XL C implements optimizations based on restrict on the Power architecture. By running a modified Livermore benchmark consisting of different loops that are suitable for restrict based optimizations we show that all three compilers are capable of doing restrict based optimizations. Furthermore we investigate loops using a pipeline simulator in order to understand the performance characteristics of the optimizations. We show that the performance for each loop vary by compiler, some loops have their running time significantly reduced while others, somewhat surprisingly, actually have their run time increased. Finally we provide some general suggestions for programmers and compiler developers on how to best use restrict.

Kl 14.15: Performance analysis and improvement of PostgreSQL

Författare/Authors: Martin Lindblom, Fredrik Strandin

Handledare/Supervisor: Jonas Skeppstedt (LTH)

Examinator/Examiner: Per Andersson (LTH)

Lokal/Room: E:2405

Abstract:

PostgreSQL is a database management system, used in many different applications throughout the industry. As databases often are the bottlenecks in the performance of applications, the performance of the database becomes crucial. Better performance can either be achieved by using more hardware, or by making the software more efficient. In this master thesis we do a performance analysis of the PostgreSQL database server from the perspective of compiler optimizations, file systems and software prefetching. We will also show how a data structure used in PostgreSQL can benefit from manually introducing software prefetching, as it is hard for the compiler to predict and insert these instructions in a profitable way.

Kl 15.15: Video Conferencing - Session and Transmission Control

Författare/Authors: Marcus Carlberg, Christoffer Stengren

Handledare/Supervisor: Jimmy Rubin (AXIS)

Examinator/Examiner: Mathias Haage (LTH)

Lokal/Room: E:2405

Abstract:

Axis Communications wants to see if it is possible to use their network surveillance cameras to set up a video conference. They would also like to know which techniques are used today to ensure optimized bandwidth usage and as good quality as possible even if the network bandwidth changes. An implementation of such a service has been made in this thesis which uses three different TCP congestion avoidance algorithms. They monitor and evaluate the network quality to adapt the video stream rate accordingly. One algorithm is only based on packet loss and is used as a baseline. The other two uses packet loss in conjunction with round trip time (RTT) to evaluate the network. The user experience was deemed better than not using the algorithms and the algorithms that was based on both packet loss and RTT was deemed superior. There are however still a few things to adapt in the camera software and hardware before a complete system can be developed.